In situ method of producing oil from oil shale



United States Patent {1113543338 [72] Inventor Harry W- Parker 3,233,670 2/1966 Thompson et a1. 166/11 BllflQSVillt, OHI- 3,241,611 3/1966 Dougan 166/40X [21] App]. No. 641,815 3,342,257 9/1967 Jacobs et a1. 166/36 [2 1 Filed d 322. 3% OTHER REFERENCES [45 1 Pateme Hill; George R. et a1. Direct Production of a Low Pour Point [731 Asslgn gaf l-iigh Gravity Shale 011. In 1. & E. c. Product Research &

"" Development, 6(1), Mar. 1967, 52- 59. TP 1 1532 Johnson; Gerald W., et a1. Non-Military Uses of Nuclear Ex- SHALE Lombard, D. B. Recovering 011 From Shale w1th Nuclear achimgznnwins Figs Explosives. 1n J. Petroleum Technology, 15(8), Aug., 1965, 52 us. c1 166/256. pp. 877- 882.

166/266, 166/272 1 [51] In 43/24 Pnmary Examiner-Charles E. O Connell 50 Field ofScarch 166/2 7 1 1, 36,40, 256, 272, 265-267, 303, 247; 208/11 and @1183 [56] cm ABSTRACT 011 is produced from a subsurface mass of frac- UNITED STATES PATENTS tured oil shale by injecting high heat capacity hydrocarbon 3.353.756 12/1967 vogel 166/7 gases to educe hydrocarbons from the shale. Produced high 3 7/1922 Hoover 8! 66/ heat capacity hydrocarbon gases are recycled to the shale ,937 3/1961 Kiel mass. High heat capacity hydrocarbon gases from a second, 3,040,809 6/1962 Pe et-"- 166/40 previously retorted shale mass can be used to initiate the educ- 3,044,545 1 962 Tooke 1156/1 1 tion of hydrocarbons, or as fuel. Products of combustion from 3,109,731 Nallflnd 203/11X the second shale mass can be used to compress and heat the 3,1 13,620 12/1963 Hemminger 166/11 injection gases,

AIR s7 66/ a2 rl 7k i as k \r a 37 3, 56 v 5a 57 43c 33 FUEL GAS 2 29 I X 3 671? 55 /64 PATENTED-umzism I 3.548338 sum 1 OF 2 FUEL GAS INVENTOR.

H. W. PARKER This invention relates to a process for them situ production of oil from an oil shale stratum. In another aspect this invention relates to contacting oil shale with hot gases.

Oil is produced from oil shale by heating the shale to a temperature above about 500 F. At this. temperature kerogen, an organic substance present in the shale, decomposes or is converted to oil; In order to produce oil from oil'shale in situ, it is necessary to fracture the shale to render the processcommercially feasible. Various methods of fracturing, such as the use of explosives or hydraulic fracturing, are known in the art. Usage of nuclear devices to'fracture shale is disclosed by M.

A. Lekas and N. C. Carpenter in an article entitled Fracturranean mass 'of shale, it"is feasible to produce oil in situ therefrom by injecting hot gases at temperatures in the range of from 500 to 1000 F. In heating oil shale with hot gases, one

economic parameter is the volume of gases injected into the fractured shale mass. The volume of gases it is necessary to circulate per barrel of oil recovered is dependent upon heat capacity per unit volume of the gases circulated. This volume determines the required compressor capacityand injection well diameter, thus directly afiects the cost of the produced oil.

Accordingly it is an object of the inventionto provide an economical in situ method of producingoil from a shale stratum. a Another object of the invention is toreduce'the' volume of injected hot gases in an in situ oil production method.

Other objects and-advantages will be apparent to one skilled in the art upon consideration of .the disclosure, drawings, and appended claims. 1 f

FIG. 1 is a schematic representation partially in cross section of one embodiment of the invention.

, capacity gases.

FIG. 2 is a schematic representation of another embodiment perature is injected into the top of 'a'subterranean mass offractured shaleto educe oil therefrom. The educed liquid and vaporous hydrocarbons flow downwardly through the fractured shale and are recovered through a well bore near the bottom of the shale mass. The injected hydrocarbon gases are free of oxygen and there is no combustion within the shale mass, all heat being supplied by surface heating of the gases. The high heat capacity hydrocarbon gases utilized in the practice of the invention have a heat capacity of at least about 20 Btus per pound mol at 900 F. and include C (ethane) and heavier hydrocarbons.

in one embodiment of the invention, high heat capacity hydrocarbon gases are separated from the recovered oil, compressed by a compressor which is powered by fuel in the form of light gases, such as methane, which is stripped from the recovered oil, heated in a furnace which burns the light gases, and recycled to the shale mass to educe' additional oil.

In another embodiment of the invention, high'heat capacity hydrocarbon gases which are separated from the shale oil recovered from a first fractured massare compressed and heated prior to being reinjected into the mass by utilizing hot gases from a second subterranean mass of fractured shale. In this embodiment, air or other oxygen containing gas is injected into the bottom of a second mass of fractured shale which has been previously retorted with hot gases, to displace hot gases from the mass. The oxygen supports combustion of coke and residual hydrocarbons in the previously retorted shale to provide additional heat. l-lot gases, including those used to initially retort the second mass and those resulting for subsequent combustion, are recovered from the second mass. The high heat capacity gases used in the initial retorting of the previously retorted mass can be used to initiate retorting in the first mass. The combustion gases are used as fuel for compressing and heating of the high heat capacity hydrocarbon gases which are recycled to the first shale mass. This provides a method of recovering oil which is entirely self-sufficient energy-wise.

Referring now to FIG. I, the top of amass 10 of shale rubble, resulting from the detonation of a nuclear device in a shale formation lll, is penetrated by a borehole 12. The shale rubble 13 extends from a solidified melt zone 14 at the bottom of the mass substantially to the top of the mass, leaving a void space 16 formed by settling of the rubble. A borehole 17 extends into the lower portion of mass 10 and is provided with a tubin'g string 18 and a down hole pump 19. The surface equipment for separating the high heat capacity hydrocarbon gases from the recovered shale oil includes an absorption'unit 23, stripping units 27 and 341, and associated equipment and conduits. A compressor 32 and a furnace 41 are provided for compressing and heating the high heat In the practice of the invention, hot gases are injected through borehole l2 downwardly through the mass 10. The temperature of the heating gases is high enough to produce the desired kerogen decomposition but low enough to minimize endothermal decomposition and fusion of carbonate minerals in the shale. Generally, gas temperatures in the range 'of from 750 to 950 F. will produce the desired kerogen decomposition.

The rate and pressure at which thehot gases are injected into the fractured shale mass is dependent upon the composi tion of the oil shale, the composition of the hot gases, and particle size distribution of the mass of rubble. Generally the pressure will be above 15 p.s.i. i

As the kerogen is decomposed, educed oil (liquid and vapor) flows by gravity drainage through rubble l3, collecting in the bottom of the mass above solid melt zone 14 and are recovered through tubing 18 by means of pump 19. The product hydrocarbons are passed through tubing 18 to a liquid-vapor separator 21 wherein a first separation is effected.

Vapor products, including noncondensable gasessuch as carbon dioxide, light hydrocarbon gases and entrained liquid droplets are passed from separator 21 through conduit 22 to an absorber 23, wherein ethane and heavier hydrocarbon gases are absorbed from the shale gas stream. The stripped shale gasstream including methane is removed overhead via conduit 24 from absorber 23. Absorber oil is circulated through conduit 26 to a stripper 27 wherein the oil is heated to strip out the high heat capacity hydrocarbon gases which are absorbed from the shale gas. The stripped absorption oil is cooled in heat exchanger 28 and passed via conduit 29 back into absorber 23. High heat capacity hydrocarbon gases including C and heavier hydrocarbons are removed overhead from stripper 27 and passed through conduit 3! to a c0mpressor 32.

Liquid shale oil is removed from separator 21 and passed through conduit 33 to a stripper 34 wherein the shale oil is heated and stripped of its high heat capacity hydrocarbon gases. The degassed shale oil is passed through conduit 36 to further processing or storage. The gases are removed overhead from stripper 34 and flow through conduit 37 to conduit 31 where they are admixed with the gases flowing from stripper 27.

In certain instances it may be advantageous (desirable) to pass a portion of the shale gas from separator 2i through conduit 38 to the intake of compressor 32. This allows control of the volume of hot gases to be injected which is independent of the volume of high heat capacity hydrocarbon gases stripped from the oil. Alternatively, the conditions in strippers 34 and 27 can be regulated to obtaina desired volume. of high heat capacity gas.

From compressor 32, the gases are passed through conduit 39 to furnace 41. Stripped shale gas is passed through conduit 42 to furnace 41 as fuel. After being heated to a predetermined high temperature, the gases are passed through conduit 43 to borehole l2 and recycled to the rubble mass 10.

Referring now to FIG. 2, additional energy .is supplied to the system illustrated in FIG. 1 by injecting air or oxygen-containing gas into a second mass 50 of shale rubble 51 which has been previously retorted by hot gas injection method described in conjunction with FIG. 1. Air is injected through borehole 52 into the lower portion of mass 50. The shale rubble 51 will be hot enough so that spontaneous combustion oc-' curs. The resulting combustion gases displace the high heat capacity gases which were used in the initial retorting of mass 50 upwardly through the mass. These gases are recovered through a borehole 53 and passed via conduits 55, 54 and 22 to the absorber 23, providing a readily available source of high heat capacity hydrocarbon gases whichcan be used to initiate eduction of oil from mass 10. A portion of these gases can be used as fuel, supplying the power requirements of the process equipment.

When the high heat capacity hydrocarbon gases are exhausted from mass 50 the entire flow through borehole 53 can be passed through conduit 55 to a combustor 56. Air is supplied to the combustor via conduit 57. The high temperature combustion products from combustor 56 are passed via conduit 58 through a gas turbine 59 to generate mechanical power. The mechanical energy can be transmitted by means of a drive shaft 61 to power compressor 32. Another drive shaft 62 powers an air compressor 63 which supplies air to conduit 57 and to conduit 64 which communicates with wellbore 52. Exhaust gases from turbine 59 are passed via conduit 66 to a heat exchanger 67 wherein they are'used to heat the compressed injection gases passing from compressor 32 through conduit 39. The heated injection gases are removed from heat exchanger 67 through conduit 43 and passed through wellbore 12 into mass 10.

Not only do the high heat capacityhydrocarbon gases reduce the volume of gas necessary to heat a given volume of oil shale, but they act as solvents as they travel through the mass of shale rubble and facilitate oil production by this action. Additionally olefins in the hydrocarbon gases such as ethylene and propylene will react with the kerogen decomposition products and enhance the quality of the oil recovered. It is apparent that the process of the invention makes maximum utilization of the gases produced from in situ retorting of oil shale, thus reducing the cost of recovering oil from oil shale.

Reasonable modification and variation are within the scope of the invention which sets forth a novel in situ method of recovering oil from oil shale.

I claim:

1. A process for producing oil from an underground deposit of oil shale having therein a first subterranean mass of fractured oil shale and a second subterranean mass of fractured oil shale, said first mass having a first borehole communicating with the top thereof and a second borehole communicating with the lower portion thereof, a said process comprising the steps of:

heating and injecting through said first borehole hydrocarbon gases having a heat capacity of at least Btus per pound mol into the top of said first mass to heat and educe liquid and vaporous hydrocarbons from said first mass;

recovering educed hydrocarbons through said second bore hole;

separating from said educed hydrocarbons-gases having a heat capacity below 20 Btu s per pound mol, gases having a heat capacity of at least 20 Btu's per pound mol, and a desired oil;

heating and reinjecting said gases having a heat capacity of at least 20 Btu's per pound mol through said first s l in ecting into said second subterranean mass sufficient oxygen-containing gas to support combustion of coke and residual hydrocarbons contained therein;

recovering combustion products from said second subterranean mass; and

utilizing said combustion products as fuel to heat and compress said hydrocarbon gases injected into said first subterranean mass.

2. A process according to claim 1 wherein hydrocarbon gases having a heat capacity of at least 20 Btu s per pound mol are also recovered from said second subterranean mass and at least a portion of said recovered hydrocarbons from said second mass are utilized as at least a portion of said hydrocarbon gases injected into said first mass.

3. A process for producing oil from an underground deposit of shale oil having a first subterranean mass of fractured oil shale rubble having a first borehole communicating with the top of said first mass and a second borehole communicating with the lower portion of said mass comprising the steps of:

heating and injecting through said first borehole hydrocarbon gases having a heat capacity of at least 20 Btu's per pound mol into the top of said first mass of oil shale rubble to heat and educe liquid and vaporous hydrocarbons from said first mass;

passing said injected hydrocarbons together with said educed liquid and vaporous hydrocarbons downwardly through said first mass of oil shale rubble;

recovering said educed liquid and vaporous hydrocarbons through said second borehole;

separating from said recovered educed hydrocarbons gases having a heat capacity below 20 Btu's per pound mol, gases having a heat capacity of at least 20 Btu's per pound mol, and a desired oil, said separation being effected by passing said recovered educed liquid and vaporous hydrocarbons from said second borehole into a vaporliquid separation zone to separate said liquid and said vaporous hydrocarbons;

passing said separated liquid hydrocarbons to a first stripper zone;

in said first stripper zone, heating and stripping from said liquid hydrocarbons a first stream of gases having a heat capacity of at least 20 Btu 5 per pound mol;

passing said separated vaporous hydrocarbons from said liquid-vapor separation zone to an absorption zone;

in said absorption zone, contacting said vaporous hydrocarbons with an absorption oil to absorb gases having a heat capacity of at least 20 Btu 5 per pound mol;

venting from said absorption zone said gases having a heat capacity below 20 Btu s per pound mol;

passing rich absorption oil from said absorption zone to a second stripper zone;

in said second stripper zone, heating and stripping from said rich absorption oil a second stream of gases having a heat capacity of at least 20 Btus per pound mol;

combining said first and second streams of gases having a heat capacity of at least 20 Btus per pound mol; and

heating and reinjeeting said combined stream of gases having a heat capacity of at least 20 Btu's per pound mol through said first borehole. 

